Fill in missing point in grid
Standard way is to remove tha Ngon face and use Grid Fill to fill in with quads. Another a bit less fast way is to use either Connect Vertex Path tool (J) or Knife tool (K) to cut edges according to existing geometry.

However there might be another way without removing that face:


Press Alt+P to poke faces.
Press Alt+J to convert tris to quads.




Note that it depends on geometry what resulting topology you will get. Also note - Grid Fill restores the curvature of the filled surfaces, this way doesn't.